1. Field
The present disclosure relates generally to electrical power systems and, in particular, to electrical power systems on aircraft. Still more particularly, the present disclosure relates to a method and apparatus for transferring electrical power provided for a load between different electrical power sources and to a transformer rectifier unit for converting alternating current power to direct current power.
2. Background
Various systems and devices on an aircraft may use electrical power. For example, without limitation, electrical power may be used by a flight control system, in-flight entertainment systems, computers, actuators, lights, fans, pumps, or other systems and devices on an aircraft. Some systems and devices on an aircraft may use direct current, DC, power. Other systems and devices on an aircraft may use alternating current, AC, power.
Electrical power for systems and devices on an aircraft may be provided by an electrical power system. An electrical power system on an aircraft may include various sources of electrical power and various structures for delivering electrical power from the electrical power sources to various systems and devices on the aircraft. An electrical power system on an aircraft may include a number of sources of AC power, a number of sources of DC power, or both. For example, without limitation, electrical power may be delivered from various power sources to various systems and devices that use electrical power on an aircraft via a number of buses. For example, AC power may be provided from a number of AC power sources to systems and devices on the aircraft that use AC power via a number of AC buses on the aircraft. DC power may be provided from a number of DC power sources to systems and devices on the aircraft that use DC power via a number of DC buses on the aircraft.
AC power on an aircraft may be provided by a number of generators, by a number of other appropriate AC power sources, or by various combinations of AC power sources. Generators for providing AC power on an aircraft may be driven by the aircraft engines, in another appropriate manner, or in a combination of appropriate manners.
An AC-to-DC converter may be one example of a source of DC power on an aircraft. AC power may be converted to DC power by a number of AC-to-DC converters on an aircraft. For example, without limitation, an AC-to-DC converter may be configured to receive AC power provided on an AC bus on the aircraft by an AC power source and to provide DC power on a DC bus on the aircraft. An AC-to-DC converter on an aircraft may be configured to provide DC power at a desired voltage for use by various systems and devices that use DC power on the aircraft from the AC power provided on the AC bus lines by the AC power source.
A battery may be another example of a source of DC power on an aircraft. A battery on an aircraft may provide DC power at a certain voltage. A DC-to-DC converter on the aircraft may be configured to convert DC power provided by the battery at a first voltage to DC power at a second voltage that is desirable for use by various systems and devices that use DC power on the aircraft. For example, a DC-to-DC converter on an aircraft may be connected to provide DC power at a desired voltage onto a DC bus on the aircraft to distribute the DC power to various systems and devices on the aircraft via the DC bus.
DC power for various systems and devices on an aircraft may be provided on a DC bus on the aircraft by different DC power sources at different times. For example, without limitation, DC power may be provided on a DC bus on an aircraft by an AC-to-DC converter at times when the aircraft engines are operating and the AC-to-DC converter is receiving AC power from a generator driven by an aircraft engine. At other times, DC power may be provided on the DC bus on the aircraft by a DC-to-DC converter receiving DC power from a battery or another source of backup power. Therefore, at various points in time, it may be desirable to change from providing power on a DC bus on an aircraft by an AC-to-DC converter to providing power on the DC bus the aircraft by a DC-to-DC converter, and vice versa.
It may desirable that transferring the providing of power on a DC bus on an aircraft between different DC power sources does not affect the DC power provided to aircraft systems and devices via the DC bus in an undesired way. Currently, transferring the providing of power on a DC bus on an aircraft between different DC power sources may result in an undesired break in the power provided on the DC bus. A method and apparatus for transferring the providing of power on a DC bus between different DC power sources without a break in power on the DC bus may be desirable.
An AC-to-DC converter on an aircraft may be implemented as a transformer rectifier unit. A transformer rectifier unit comprises a transformer and a rectifier. For example, without limitation, a transformer in a transformer rectifier unit on an aircraft may be configured to transform a multiple-phase AC input signal provided by an AC power source to a multiple-phase AC output signal. The transformer may be configured to transform the voltage, phase, other characteristics, or various combinations of characteristics of the multiple-phase AC input signal received by the transformer to provide the multiple-phase AC output signal. The rectifier in the transformer rectifier unit may be configured to convert that multiple-phase AC output signal provided by the transformer in the transformer rectifier unit to a DC power signal.
It may be desirable that the quality of the DC power provided by a transformer rectifier unit on an aircraft is adequate. For example, without limitation, it may be desirable that voltage ripple in the DC power signal provided by a transformer rectifier unit is reduced. It also may be desirable to simplify the design of a transformer rectifier unit on an aircraft.
Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.